there is no climate emergency – letter

With Global Warming protests and strikes held by student in a number of countries, a group of 500 scientists and other “professionals in climate and related fields” have written an open letter to the United Nations . In the letter, the signatories state that “climate science should be less political, while climate policies should be more scientific,” while also denouncing “the uncertainties and exaggerations in…predictions of global warming.” The text is reproduced below and the full letter available for download.

A polar bear in Repulse Bay, Nunavut Territory, Canada.
Paul Souders | Getty Images

There is no climate emergency

A global network of 500 scientists and professionals has prepared this urgent message. Climate science should be less political, while climate policies should be more scientific. Scientists should openly address the uncertainties and exaggerations in their predictions of global warming, while politicians should dispassionately count the real benefits as well as the imagined costs of adaptation to global warming, and the real costs as well as the imagined benefits of mitigation.

Natural as well as anthropogenic factors cause warming

The geological archive reveals that Earth’s climate has varied as long as the planet has existed, with natural cold and warm phases. The Little Ice Age ended as recently as 1850. Therefore, it is no surprise that we now are experiencing a period of warming.

Warming is far slower than predicted

The world has warmed at less than half the originally-predicted rate, and at less than half the rate to be expected on the basis of net anthropogenic forcing and radiative imbalance. It tells us that we are far from understanding climate change.

Climate policy relies on inadequate models

Climate models have many shortcomings and are not remotely plausible as policy tools. Moreover, they most likely exaggerate the effect of greenhouse gases such as CO2. In addition, they ignore the fact that enriching the atmosphere with CO2 is beneficial.

CO2 is plant food, the basis of all life on Earth

CO2 is not a pollutant. It is essential to all life on Earth. Photosynthesis is a blessing. More CO2 is beneficial for nature, greening the Earth: additional CO2 in the air has promoted growth in global plant biomass. It is also good for agriculture, increasing the yields of crops worldwide.

Global warming has not increased natural disasters

There is no statistical evidence that global warming is intensifying hurricanes, floods, droughts and suchlike natural disasters, or making them more frequent. However, CO2-mitigation measures are as damaging as they are costly. For instance, wind turbines kill birds and bats, and palm-oil plantations destroy the biodiversity of the rainforests.

Climate policy must respect scientific and economic realities

There is no climate emergency. Therefore, there is no cause for panic and alarm. We strongly oppose the harmful and unrealistic net-zero CO2 policy proposed for 2050. If better approaches emerge, we will have ample time to reflect and adapt. The aim of international policy should be to provide reliable and affordable energy at all times, and throughout the world.


Galactic Colonization: A New Model

2D slice of 3D simulation of expansion of the Galactic Settlement front. Blue is unsettled, red is settled and green is targeted

Jonathan Carroll-Nellenback and partners have published a fine article in Astrophysical Journal on a modelling exercise on civilizational expansion across the Milky Way, addressing the Fermi Paradox. According to a study published last month in The Astronomical Journal, extraterrestrial life might be taking its time to fully explore the galaxy, even using the movement of star systems to make this type of journey easier.

The Fermi Paradox has a long history in discussions of the prevalence of “alien” technological civilizations (i.e. ‘exo-civilizations’) in the galaxy. Originating with a lunchtime conversation in 1950 where Enrico Fermi famously asked ‘where is ev­erybody?’, the Fermi paradox was first for­malized in 1975 and has since become a standard framework for addressing questions concerning the preva­lence of exo-civilizations. Formally the paradox might be expressed as follows: “If technologically advanced exo-
civilizations are common, then we should already have evidence of their existence either through direct or in­direct means”

Assuming amongst other things that any interstellar probe would have a minimum velocity of 30km/sec which would be achievable using gravity assist from large planets within 1 AU they reach a number of interesting conclusion:

  • When diffusive stellar motions are accounted for, they contribute to the Galaxy becoming fully set­tled in a time less than, or at very least comparable to its present age, even for slow or infrequent in­terstellar probes;
  • If a settlement front forms, all settleable systems behind it become “filled in” in a time less than the current age of the Galaxy;
  • While settlement wave crossing and fill-in times are short, consideration of finite civilization lifetimes in a steady state model allows for conditions in which the settled fraction is less than 1. Thus the galaxy may be in a steady state in which not every settleable system is currently settled.
  • Statistical fluctuations in local density of settleable systems allows for the formation of set­tlement clusters which can continually resettle one another. These clusters are then surrounded by large unsettled regions. If such conditions repre­sent the situation in our region of the galaxy and Earth was not in one of the ”re-settlement” clusters it would be highly probable that we would not have been settled (or visited) by another civilization for some time.
  • By consideration of the convolution of steady state solutions with geologic evidence horizons, it is pos­sible to find situations in which Earth may not have experienced a settlement event for longer than some horizon time (assumed to be 1 Myr) even though the galaxy supports a population of inter­stellar civilizations.

Even for slow probes (30 km/sec) they find that the upper limit of the galactic crossing times are just less than 1 Gyr. This is in accord with our modelling for the colonization of the Type A stars within 100 LY of Earth assuming 5 habitable planets amongst the 75 stars that meet this criteria. We estimated that dependent on probe speed would take between 350,000 and 900,000 years.

The authors discuss amongst other things the energy requirements for interstellar travel and suggest that this is a major impediment to the postulated wave of colonization. A multi-generational ship would they suggest require economies equivalent to that of entire solar systems. They consider a ‘medium multi-generational cruiser’ case . This would be a ship traveling at v = 0.05c, carrying a population of 104 people and weighing 107 tonnes. Such a ship would require a power of 6900 zettajoules (ZJ) funded by a solar sys­tem wide civilization of 900 billion people that would generate 1136 ZJ per year. The world presently produces around 1 ZJ Joule and this quantum of energy would require a significant civilizational commitment.

Download the Full Text

The Fermi Paradox and the Aurora Effect: Exo-civilization Settlement, Expansion and Steady States

Jonathan Carroll-NellenbackAdam FrankJason WrightCaleb Scharf(Submitted on 12 Feb 2019)

We model the settlement of the galaxy by space-faring civilizations in order to address issues related to the Fermi Paradox. We explore the problem in a way that avoids assumptions about the intent and motivation of any exo-civilization seeking to settle other planetary systems. We first consider the speed of an advancing settlement via probes of finite velocity and range to determine if the galaxy can become inhabited with space-faring civilizations on timescales shorter than its age. We also include the effect of stellar motions on the long term behavior of the settlement front which adds a diffusive component to its advance. The results of these models demonstrate that the Milky Way can be readily ‘filled-in’ with settled stellar systems under conservative assumptions about interstellar spacecraft velocities and launch rates. We then consider the question of the galactic steady-state achieved in terms of the fraction of settled planets. We do this by considering the effect of finite settlement civilization lifetimes on the steady states. We find a range of parameters for which the galaxy supports a population of interstellar space-faring civilizations even though some settleable systems are uninhabited. Both results point to ways in which Earth might remain unvisited in the midst of an inhabited galaxy. Finally we consider how our results can be combined with the finite horizon for evidence of previous settlements in Earth’s geologic record. Our steady-state model can constrain the probabilities for an Earth visit by a settling civilization before a given time horizon. These results break the link between Hart’s famous “Fact A” (no interstellar visitors on Earth now) and the conclusion that humans must, therefore, be the only technological civilization in the galaxy.

Arc/Info Binary Grid import

I have had occasional issues with the import of Arc/Info Binary Grid format files into ARCGIS. The solution is all too easy. The import script is legacy and relies on the oldest of ARCGIS file and directory formatting requirements, no spaces. No spaces in parent directories or file names. The naming convention in ARCGIS is really quite annoying at times.